Wednesday, April 6, 2011

Leveling the X-axis and the Bed

Tonight's main focus was on leveling the X-axis and the bed to try to correct this continual Z-offset that keeps occurring. Last nights attempt to adjust the Z-flag had helped but it was still occurring.

I started by verifying that the Y-rods were level, which they were. Then I used those as a reference to measure the distance between the X-rods. There was a delta between the two ends of a few tenths of mm. Given that 0.1mm variation in extruder height can make a difference between good first layer adhesion and not, this needed to be corrected.

I loosened the tensioning pulley on the Z-belt and manually adjusted each Z-screw until the reading on the calipers was the same for each Y-rod to front X-rod distance. Then I tightened everything back up making sure that nothing moved. When it was all back together I reverified the measurements to make sure nothing had moved.

I then used a similar technique to set the height of the bed from the Y-rods. This was a loooong process as each adjustment changed the other spring heights slightly. Once they were all the same I could proceed to verify the bed against the extruder nozzle. It was fairly level now, but did require some minor adjustments to bring the separation between the nozzle and bed even in all corners.

I also discovered something interesting with the printed 'W' bed springs. They don't apply even force to the bed. I had them running parallel with the bed, but I found that on the top of the spring was not always flat and applied more pressure either before the bolt or after (depending on how the top was distorted), changing the bed height very slightly. I decided to rotate the springs 90-degrees to be perpendicular to the bed, so their top surface has less contact along the length of the bed. This appears to help these slight bed distortions.

I then was able to get on to some more test prints. I dialed down the flow rate to 1200 (from 1300), the print quality was very good. Possibly one of the best to date. The first layer still had too much flow, so I may need to play with the first layer settings. As the print went on, the higher layers got more ropey, I put that down to how I have my spool of filament. It doesn't turn very easily and after some time printing the force required to pull filament off the spool is too much for the extruder - unless I manually turn the spool a bit. Must get a better spool!

The print continued to pause nearly every layer - just like last night, so I did roll-up my sleeves and dive into the G-Code. Skeinforge appears to be generating the deprecated M108 code (old code to control the extruder). A quick search and replace removed them all and the GCode printed without issues. I need to add M108 to my replace file.

I also updated my Gen6 Firmware to the latest version that came out earlier this year. Tomorrow I'll write a detailed article on how to upgrade the firmware and some of the changes I made (these for my own benefit so I can figure out how to do it again when the next release comes out!)